The present invention relates to the field of soldering, in particular to forming stable solder bonds between conductive pads.
Conventional solder bonds are created between components such as optoelectronic devices by heating the solder and devices under an applied force and allowing the solder to cool. The applied force and the heating of components may form solder balls and wicking of the solder onto the components. This may cause an unintentional short circuit between the components. A solder bond in a compressive state is susceptible to creep which undesirably shifts the alignment between the devices. Further, conventional solder bonds may also be formed between a substrate and component without the application of force or physical stops thereto. Upon heating and solder reflow of such conventional solder bonds, surface tension will cause the solder to minimize the surface area to volume ratio. Thus, a bond that is in equilibrium (not compression or tension) will be formed. Accordingly, a need exists for a solder bonding system and method that results in a stable solder bond in a tensile state preventing the devices bonded from being realigned.
An aspect of the present invention provides a solder bonding system that includes a substrate having a recess and a conductive pad disposed in the recess of the substrate. The solder bonding system also includes a solder pad contacting the conductive pad. In an exemplary embodiment, the solder pad has a width greater than the width of the conductive pad.
Another aspect of the present invention provides a method for forming a solder bond between a first conductive pad of a substrate and a second conductive pad of a component. The method includes providing the first conductive pad in a recess of the substrate and providing a solder pad on the first conductive pad. In an exemplary embodiment, the width of the solder pad is greater than the width of the first conductive pad. The method also includes heating the solder pad to form the solder bond and joining the first and second conductive pads. The solder bond formed has an inverse meniscus around a circumference of the solder bond.